An experimental study of forced vibration on natural convection between closed ended concentric and eccentric annular of horizontal cylinder

An experimental study has been done into the effects of vertical mechanical vibrating, vertical eccentricity, and the Rayleigh number on natural convection heat transferring out of a horizontally enclosed, ending cylindrical annulus with a radius rate of 2.6 and an aspect ratio of (2:1). The annulus produced between two concentric and vertically eccentric circular cylinders is positioned horizontally, and its internal wall is uniformly heated while isothermally cooling the external wall. The range of present conditions for Rayleigh number is 5×〖10〗^4≤Ra≤6.48×〖10〗^6 , and Pr= 0.703, the frequency of vibration is 0f 20Hz; and the amplitude is b mm), with possible exclusion of the highest positive and negative eccentricities. Plots of the average Nusselt number variation against the Rayleigh number showed a significant increase in negative vertical eccentricity. It was found that the average Nusselt decreased as the internal cylinder changed its location vertically from negative to positive through the center, which is normally a desirable effect, but has no advantage over the concentric on the positive side. However, an increase in the Rayleigh number leads to a nearly proportional increase in the average Nusselt number and a smaller yet still substantial increase in positive eccentricity.